The Experts below are selected from a list of 10548 Experts worldwide ranked by ideXlab platform
Pekka Kalevi Vallittu - One of the best experts on this subject based on the ideXlab platform.
-
The effect of span length of Flexural Testing on properties of short fiber reinforced composite
Journal of Materials Science: Materials in Medicine, 2012Co-Authors: Sufyan Garoushi, Lippo Veli Juhana Lassila, Pekka Kalevi VallittuAbstract:The aim of this study was to determine the effect of different span lengths of Flexural Testing on some properties of test specimens made of experimental short fiber reinforced composite resin (FC). Bar shaped specimens with different lengths were made from experimental FC composite with an average fiber length of 3 mm and particulate filler composite (PFC, control: Z250). The specimens ( n = 8) were polymerized with a hand light-curing unit for 40 s and dry stored in a room temperature for 24 h before Testing. Three-point Flexural test for determination of ultimate Flexural strength, toughness and Flexural modulus of specimens was made with different span lengths (20, 15, 10, 7, 6, 5 mm) with a speed of 1.0 mm/min until fracture. By shortening the span length for specimens made of FC or PFC, the Flexural modulus decreased (from ca. 11 to 4 GPa) and Flexural toughness increased (from ca. 0.25 to 2.25 MPa). Reduction in Flexural strength by shortening the span length was found with PFC (from 170 to 125 MPa) but not with FC, which showed reduction by span lengths from 20 to 7 mm and considerable increase of Flexural strength by further shortening the span length from 7 to 5 mm. Shortening of span length of Flexural Testing showed linear reduction of the measured and calculated Flexural properties of PFC and some properties of FC, but Flexural strength values for FC were non-linearly related to the span length: the highest values were obtained with the longest and the shortest span lengths. In reporting the Flexural values of composites, the span length—specimen dimension ratio, and the length of the reinforcement need to be taken into consideration.
-
acoustic emission analysis of fiber reinforced composite in Flexural Testing
Dental Materials, 2004Co-Authors: Pasi Alander, Lippo Veli Juhana Lassila, Arzu Tezvergil, Pekka Kalevi VallittuAbstract:OBJECTIVES: The aim of this study was to examine the emission of acoustic signals from six commercially available fiber-reinforced composites (FRC) used in the frameworks of fixed partial dentures in material bending. METHODS: FRC test specimens were made of six commercially available fiber products of polyethylene or glass and five light-curing resins. FRC test specimens were polymerized with a hand light-curing unit or with a light-curing oven. The Flexural test for determination of ultimate Flexural strength of test specimens (n = 6) was based on the ISO 10477 standard after the specimens were stored in air or in water for two weeks. The acoustic emission (AE) signals were monitored during three-point loading test of the test specimens using a test with increasing loading levels until the specimens fractured. RESULTS: Generally, stress level required for the AE activity initiation ranged from 107 MPa (Ribbond) to 579 MPa (everStick). The ultimate Flexural strength of FRC specimens were higher, ranging from 132 to 764 MPa, being highest with everStick and Vectris FRC, and lowest with Ribbond FRC. ANOVA showed a statistically significant difference between the initiation of AE activity and the ultimate Flexural strength according to the brand (p < 0.001) storing conditions (p < 0.001) and polymerization procedure (p < 0.001). AE activity and ultimate Flexural strength correlated significantly (p < 0.010, r = 0.887). SIGNIFICANCE: The result of this study suggested that AE activity in FRC specimens started at a 19-32% lower stress level than occurred at final fracture.
Lippo Veli Juhana Lassila - One of the best experts on this subject based on the ideXlab platform.
-
The effect of span length of Flexural Testing on properties of short fiber reinforced composite
Journal of Materials Science: Materials in Medicine, 2012Co-Authors: Sufyan Garoushi, Lippo Veli Juhana Lassila, Pekka Kalevi VallittuAbstract:The aim of this study was to determine the effect of different span lengths of Flexural Testing on some properties of test specimens made of experimental short fiber reinforced composite resin (FC). Bar shaped specimens with different lengths were made from experimental FC composite with an average fiber length of 3 mm and particulate filler composite (PFC, control: Z250). The specimens ( n = 8) were polymerized with a hand light-curing unit for 40 s and dry stored in a room temperature for 24 h before Testing. Three-point Flexural test for determination of ultimate Flexural strength, toughness and Flexural modulus of specimens was made with different span lengths (20, 15, 10, 7, 6, 5 mm) with a speed of 1.0 mm/min until fracture. By shortening the span length for specimens made of FC or PFC, the Flexural modulus decreased (from ca. 11 to 4 GPa) and Flexural toughness increased (from ca. 0.25 to 2.25 MPa). Reduction in Flexural strength by shortening the span length was found with PFC (from 170 to 125 MPa) but not with FC, which showed reduction by span lengths from 20 to 7 mm and considerable increase of Flexural strength by further shortening the span length from 7 to 5 mm. Shortening of span length of Flexural Testing showed linear reduction of the measured and calculated Flexural properties of PFC and some properties of FC, but Flexural strength values for FC were non-linearly related to the span length: the highest values were obtained with the longest and the shortest span lengths. In reporting the Flexural values of composites, the span length—specimen dimension ratio, and the length of the reinforcement need to be taken into consideration.
-
acoustic emission analysis of fiber reinforced composite in Flexural Testing
Dental Materials, 2004Co-Authors: Pasi Alander, Lippo Veli Juhana Lassila, Arzu Tezvergil, Pekka Kalevi VallittuAbstract:OBJECTIVES: The aim of this study was to examine the emission of acoustic signals from six commercially available fiber-reinforced composites (FRC) used in the frameworks of fixed partial dentures in material bending. METHODS: FRC test specimens were made of six commercially available fiber products of polyethylene or glass and five light-curing resins. FRC test specimens were polymerized with a hand light-curing unit or with a light-curing oven. The Flexural test for determination of ultimate Flexural strength of test specimens (n = 6) was based on the ISO 10477 standard after the specimens were stored in air or in water for two weeks. The acoustic emission (AE) signals were monitored during three-point loading test of the test specimens using a test with increasing loading levels until the specimens fractured. RESULTS: Generally, stress level required for the AE activity initiation ranged from 107 MPa (Ribbond) to 579 MPa (everStick). The ultimate Flexural strength of FRC specimens were higher, ranging from 132 to 764 MPa, being highest with everStick and Vectris FRC, and lowest with Ribbond FRC. ANOVA showed a statistically significant difference between the initiation of AE activity and the ultimate Flexural strength according to the brand (p < 0.001) storing conditions (p < 0.001) and polymerization procedure (p < 0.001). AE activity and ultimate Flexural strength correlated significantly (p < 0.010, r = 0.887). SIGNIFICANCE: The result of this study suggested that AE activity in FRC specimens started at a 19-32% lower stress level than occurred at final fracture.
Ian P Bond - One of the best experts on this subject based on the ideXlab platform.
-
a self healing carbon fibre reinforced polymer for aerospace applications
Composites Part A-applied Science and Manufacturing, 2007Co-Authors: G Williams, Ray Trask, Ian P BondAbstract:Self-healing is receiving increasing interest worldwide as a technology to autonomously address the effects of damage in composite materials. This paper describes the results of four point bend Flexural Testing (ASTM-D6272-02) of T300/914 carbon fibre reinforced epoxy with resin filled embedded hollow glass fibres (HGF) which provided a self-healing functionality. The study investigated the effect of the embedded HGF on the host CFRP mechanical properties and also the healing efficiency of the laminates after they were subjected to quasi-static impact. Specimens were tested in the undamaged, damaged and healed conditions using a commercial two-part epoxy healing agent (Cytec Cycom 823). Microscopic characterisation of the embedded HGF was also undertaken to characterise the effect on the host laminate fibre architecture.
-
Bioinspired self-healing of advanced composite structures using hollow glass fibres
Journal of the Royal Society Interface, 2007Co-Authors: Ray Trask, G. J. Williams, Ian P BondAbstract:Self-healing is receiving an increasing amount of worldwide interest as a method to autonomously address damage in materials. The incorporation of a self-healing capability within fibre-reinforced polymers has been investigated by a number of workers previously. The use of functional repair components stored inside hollow glass fibres (HGF) is one such bioinspired approach being considered. This paper considers the placement of self-healing HGF plies within both glass fibre/epoxy and carbon fibre/epoxy laminates to mitigate damage occurrence and restore mechanical strength. The study investigates the effect of embedded HGF on the host laminates mechanical properties and also the healing efficiency of the laminates after they were subjected to quasi-static impact damage. The results of Flexural Testing have shown that a significant fraction of Flexural strength can be restored by the self-repairing effect of a healing resin stored within hollow fibres. © 2006 The Royal Society.
-
a hollow fibre reinforced polymer composite encompassing self healing and enhanced damage visibility
Composites Science and Technology, 2005Co-Authors: Jody W.c. Pang, Ian P BondAbstract:Abstract The aim of this study was to develop a novel fibre reinforced plastic which employed a biomimetic approach to undertake self-repair and visual enhancement of impact damage by a bleeding action from filled hollow fibres. The results of Flexural Testing have shown that for the lay-up investigated, a significant fraction of Flexural strength lost after impact damage can be restored by the self-repairing effect of a healing resin stored within hollow fibres. The release and infiltration of an UV fluorescent dye from fractured hollow fibres into damage sites within the internal structure of the composite has been successfully demonstrated. It has been correlated with respect to the ultrasonic C-scan NDT/NDE technique and shown to be an effective method of quickly and easily highlighting damage at the surface that requires further investigation. This could be of particular benefit where rapid visual inspection of large surface areas (e.g., wing skins) is required.
-
A hollow fibre reinforced polymer composite encompassing self-healing and enhanced damage visibility
Composites Science and Technology, 2005Co-Authors: Jody W.c. Pang, Ian P BondAbstract:The aim of this study was to develop a novel fibre reinforced plastic which employed a biomimetic approach to undertake self-repair and visual enhancement of impact damage by a bleeding action from filled hollow fibres. The results of Flexural Testing have shown that for the lay-up investigated, a significant fraction of Flexural strength lost after impact damage can be restored by the self-repairing effect of a healing resin stored within hollow fibres. The release and infiltration of an U V fluorescent dye from fractured hollow fibres into damage sites within the internal structure of the composite has been successfully demonstrated. It has been correlated with respect to the ultrasonic C-scan NDT/NDE technique and shown to be an effective method of quickly and easily highlighting damage at the surface that requires further investigation. This could be of particular benefit where rapid visual inspection of large surface areas (e.g., wing skins) is required. © 2005 Elsevier Ltd. All rights reserved.
M Serna C Moreno - One of the best experts on this subject based on the ideXlab platform.
-
pseudo ductility in Flexural Testing of symmetric 45 angle ply cfrp laminates
Composites Science and Technology, 2018Co-Authors: M Serna C Moreno, Horta S Munoz, Romero A Gutierrez, C Rappold, J Martinez L Vicente, Pablo Antonio Moralesrodriguez, J Lopez J CelaAbstract:Abstract Pseudo-ductility could be sought in composite structures to avoid their brittle behaviour and, consequently, to withstand higher levels of external loading due to an extended non-linear response. This mechanism has been deeply examined in the literature for angle-ply laminates submitted to uniaxial tests. Nonetheless, the pseudo-ductile effects could appear also under Flexural loading because tension and compression are applied in different regions of the cross-sections simultaneously. In this sense, bending Testing presents a higher degree of complexity introduced by the variation of the strain through the cross-section thickness. Taking this into account the main scope of this work is to understand, describe, predict and optimise the pseudo-ductile Flexural response of symmetric ±45° angle-ply laminates consisting of unidirectional and continuous CFRP plies. The outcome of three-point bending tests is reviewed analytically and experimentally. The analytical study considers the different behaviour of the material under tension and compression as well as the neutral fibre deviation from the mid-height plane. During Testing the full normal strain field is acquired by means of a DIC system while strain-rosettes help to complete the data. The post-process based on microscopic characterization using SEM technology allows to observe the procedure of damage initiation and its evolution. Finally, the determination of the stacking sequences that minimise the bending-twisting coupling but favour the pseudo-ductile response is developed applying optimisation techniques with design purposes.
-
Flexural Testing on carbon fibre laminates taking into account their different behaviour under tension and compression
IOP Conference Series: Materials Science and Engineering, 2016Co-Authors: M Serna C Moreno, Romero A Gutierrez, J Martinez L VicenteAbstract:An analytical model has been derived for describing the results of three-point-bending tests in materials with different behaviour under tension and compression. The shift of the neutral plane and the damage initiation mode and its location have been defined. The validity of the equations has been reviewed by Testing carbon fibre-reinforced polymers (CFRP), typically employed in different weight-critical applications. Both unidirectional and cross-ply laminates have been studied. The initial failure mode produced depends directly on the beam span- thickness relation. Therefore, specimens with different thicknesses have been analysed for examining the damage initiation due to either the bending moment or the out-of-plane shear load. The experimental description of the damage initiation and evolution has been shown by means of optical microscopy. The good agreement between the analytical estimations and the experimental results shows the validity of the analytical model exposed.
Geoffrey A Thompson - One of the best experts on this subject based on the ideXlab platform.
-
determining the slow crack growth parameter and weibull two parameter estimates of bilaminate disks by constant displacement rate Flexural Testing
Dental Materials, 2004Co-Authors: Geoffrey A ThompsonAbstract:Summary Objectives. This study examined the influence of displacement-rate and relative layer heights (RLH) on the slow crack growth exponent and Weibull twoparameter estimates of bilayered ceramic composite disks composed of In-Ceram Alumina and Vitadur Alpha porcelain. Methods. Equibiaxial disks were fabricated with RLH of 1:2, 1:1 and 2:1, for InCeram Alumina and Vitadur Alpha porcelain, respectively. Ninety specimens each (30 1:2, 30 1:1, and 30 2:1) were tested in an equibiaxial ring-on-ring Testing apparatus at displacement-rates of 0.127, 1.27 and 12.7 mm min 21 . Results. Weibull parameters were statistically significantly affected by changes in RLH at a constant displacement-rate and the slow crack growth parameters were significantly affected by RLH. Many specimens exhibited nonbrittle failure modes. Nonbrittle failures usually exhibited a fall, followed by a rise in load prior to catastrophic failure, and most occurred in specimens with thicker cores at low displacement-rates. Significance. Geometries of layered materials may affect their reliability and longevity.